ENS 40356
ENS Event | |
|---|---|
09:45 Nov 25, 2003 | |
| Title | 24 Hour Nrc Bulletin 91-01 Notification Regarding Loss of Double Contingency Protection |
| Event Description | At 0420 on 11/25/03, the PSS (Plant Shift Superintendent) was notified that contrary to NCSA (Nuclear Criticality Safety Assessment) CAS-011, 'Shutdown of the Cascade With or Without Inventory', M&TE (Measuring & Testing Equipment) pressure gauges, installed on the RCW( Recirculating Cooling Water) return side of the C-331 U/3 C/2 condenser, were removed prior to the RCW supply spool piece being removed. NCSA CAS-011 requires independent verification that the supply spool piece has been removed prior to removing the M&TE gauges. The purpose of these gauges is to monitor the condenser pressure to insure RCW pressure in the condenser does not exceed 17 psig in the event the RCW supply valve leaks with the return valve completely closed. As long as the 17 psig limit is not exceeded, RCW pressure can not over come the coolant pressure and leak into the coolant.
Evolutions that occurred during the spool piece removal found that the RCW return valve to the condenser could not be completely closed. This provided an open flow path to pressure gauges installed on the RCW return header allowing for pressure readings to be taken that provides an indication of the pressure at the condenser. Pressure readings on the RCW return header indicate that the RCW return did not exceed the 17 psig as required in the NCSA. The NRC Senior Resident Inspector has been notified of this event. PGDP Assessment and Tracking Report No, ATRC-03-4076, PGDP Event Report No. PAD-2003-021, NRC Event Worksheet # 40356 Responsible Division: Maintenance SAFETY SIGNIFICANCE OF EVENTS: Double contingency was not maintained because independent verification that the supply spool piece had been removed before removing the M&TE pressure gauges was not performed. However, since the RCW return header did not exceed 17 psig, the process condition was maintained. This event was of low safety significance due to moderation control being maintained. POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIOS) OF HOW CRITICALITY COULD OCCUR: Once the fluorinating environment is removed from the process cell, moisture that may leak into the process gas side could potentially moderate a uranium deposit that may be present. RCW pressures below 17 psig will prevent water from leaking into the coolant that could then leak into the process gas side. Sufficient water would have to leak into the process gas side from the coolant and moderate a critical mass of uranium. CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC): Double contingency is maintained by implementing two controls on moderation. ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDES PROCESS LIMIT AND % WORST CASE CRITICAL MASS): This system has a process limit of [DELETED]. NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES: The first leg of double contingency is based on ensuring that a condenser tube leak will not introduce RCW (moderator) into the process gas side through the coolant. This is accomplished through monitoring the RCW return pressure to be 17 psig or less. Once the return RCW valve is closed the M&TE gauges, installed on the RCW return side of the condenser, provide indication that the condenser does not exceed 17 psig. The purpose of these gauges is to monitor the condenser pressure in the event the supply valve leaks with the return valve completely closed. Under these conditions, actions are required if the condenser pressure exceeds 17 psig. As long as the 17 psig limit is not exceeded, RCW can not over come the coolant pressure and leak into the coolant. Since the pressure gauges were removed prior to the spool piece being removed, this control was violated. However, due to the return valve leaking at the condenser, an open flow pathway is available to peak reading pressure gauges installed on the RCW return header that would provide an indication of the pressure at the condenser. Pressure readings from the RCW return header do not indicate the return pressure exceeded 17 psig. Therefore, the process parameter, moderation, was maintained. The second leg of double contingency is based on an independent verification that the supply spool piece has been removed prior to removing the M&TE pressure gauges. Since the gauges had been removed before the supply spool piece was removed, the independent verification requirement was violated. Though this control was violated, the process parameter was maintained due to the RCW return header pressure not exceeding 17 psig. Since double contingency is based on two controls on one parameter, double contingency was not maintained. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED: The M&TE pressure gauges were re-installed at approximately 0620 on 11-25-03. The licensee will notify the DOE Site Representative. |
| Where | |
|---|---|
| Paducah Gaseous Diffusion Plant Paducah, Kentucky (NRC Region 2) | |
| License number: | GDP-1 |
| Reporting | |
| Response | |
| Time - Person (Reporting Time:+11.47 h0.478 days <br />0.0683 weeks <br />0.0157 months <br />) | |
| Opened: | K. A. Beasley 21:13 Nov 25, 2003 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | Nov 25, 2003 |
| 40356 - NRC Website | |
Paducah Gaseous Diffusion Plant with Response | |
WEEKMONTHYEARENS 483982012-10-10T18:05:00010 October 2012 18:05:00
[Table view]Response Double Contingency Control for Empty Cylinders Not Maintained ENS 479112012-05-08T21:16:0008 May 2012 21:16:00 10 CFR 76.120(c)(2), Response Autoclave High Pressure Isolation System Failure ENS 474832011-11-28T15:30:00028 November 2011 15:30:00 Response 24-Hour Report Concerning a Localized Loss of a Geometry Criticality Control Contingency ENS 473102011-09-30T13:54:00030 September 2011 13:54:00 Response 24-Hour Nrc Bulletin 91-01 Report Involving a Loss of One Leg of Double Contingency ENS 471762011-08-19T13:15:00019 August 2011 13:15:00 Response 24-Hr Loss of Criticality Control Report Required Under Bulletin 91-01, Supplement 1 ENS 465922011-02-03T15:30:0003 February 2011 15:30:00 Response 24 Hour Notification Under Bulletin 91-01 Concerning Leakage of Moderating Liquid ENS 463122010-10-06T16:06:0006 October 2010 16:06:00 Response 24 Hour Notification Under Bulletin 91-01 Concerning Cooldown Verification of Uf6 Cylinders ENS 461052010-07-17T19:07:00017 July 2010 19:07:00 Response 24 Hour 91-01 Bulletin Report on Loss of One of Two Criticality Control Contingencies ENS 454922009-11-12T17:15:00012 November 2009 17:15:00 Response Violation of a Nuclear Criticality Safety Control ENS 450422009-05-04T10:07:0004 May 2009 10:07:00 Response 24 Hour 91-01 Bulletin Report on Loss of One of Two Criticality Control Contingencies ENS 445582008-10-09T20:37:0009 October 2008 20:37:00 Response 24-Hours Bulletin 91-01 Report Involving Failure to Visually Inspect Storage Cylinders ENS 442232008-05-18T22:21:00018 May 2008 22:21:00 Response Violation of a Nuclear Criticality Safety Approval - 24-Hour Report ENS 441512008-04-17T21:44:00017 April 2008 21:44:00 Response 24-Hour Nrc Bulletin 91-01 Report Involving an Excessively Large Container Found in a Fissile Control Area ENS 441002008-03-26T19:57:00026 March 2008 19:57:00 Response 24 Hour Report of Degraded Criticality Control ENS 440562008-03-11T19:57:00011 March 2008 19:57:00 Response Two Cylinders Identified with Weight Change Prior to Wash ENS 432322006-09-23T03:00:00023 September 2006 03:00:00 Response Reported Under Nrc Bulletin 91-01 24 Hour Notification ENS 421652005-11-22T18:05:00022 November 2005 18:05:00 Response Improper Criticality Spacing for Waste Drum ENS 411582004-10-29T14:45:00029 October 2004 14:45:00 Response Criticality Control Report ENS 410202004-09-04T18:45:0004 September 2004 18:45:00 Response Violation of Nuclear Criticality Safety Control in the Process Building ENS 408732004-07-14T18:00:00014 July 2004 18:00:00 Response Criticality Control 24-Hour (Bulletin 91-01) Report ENS 408602004-07-08T20:50:0008 July 2004 20:50:00 Response 24 Hour Nrc Bulletin 91-01 Loss of Criticality Control ENS 407232004-05-03T21:00:0003 May 2004 21:00:00 Response Criticality Control 24-Hour (Bulletin 91-01) Report ENS 407002004-04-23T13:45:00023 April 2004 13:45:00 Response Criticality Control 24-Hour (Bulletin 91-01) Report ENS 408052004-04-23T10:53:00023 April 2004 10:53:00 Response Paducah Gaseous Diffussion Plant - Response Bulletin 91-01 24 - Hour Report ENS 406412004-04-04T19:30:0004 April 2004 19:30:00 Response 24-Hour Nrc Bulletin 91-01 Loss of Criticality Control Notification ENS 404552004-01-16T21:27:00016 January 2004 21:27:00 Response 24 Hour Notification for Bulletin 91-01 Loss of Criticality Safety Controls Involving Waste Drum ENS 404472004-01-13T19:00:00013 January 2004 19:00:00 Response 24 Hour Notification for Bulletin 91-01 Loss of Criticality Safety Controls Involving Waste Drum ENS 403562003-11-25T09:45:00025 November 2003 09:45:00 Response 24 Hour Nrc Bulletin 91-01 Notification Regarding Loss of Double Contingency Protection ENS 401512003-09-11T13:45:00011 September 2003 13:45:00 Response Double Contingency Was Not Maintained for Non-Fissile Nams. ENS 401392003-09-07T12:50:0007 September 2003 12:50:00 Response Criticality Controls Degradation at Paducah ENS 401092003-08-27T14:00:00027 August 2003 14:00:00 Response Procedural Deficiency Omission 2012-05-08T21:16:00 | |